The plunge and then surge of commodity prices this year shows investors have spent more time watching each other than watching the fundamentals

In markets, as in life, a sudden fright can quickly be replaced by embarrassed laughter. The fear evident earlier this year has already been superceded by nervous giggling in Western equity markets, while in some areas of commodities, where the shock was deepest, it seems to have turned into full-on hysterics.

Anyone who bought back into commodities at their bottom in late January has been laughing all the way to the bank. By the end of last week, global mining shares had rebounded 75%, the strongest over a similar period...